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aa0ef6602d
Summary: In some use cases, table readers for all live files should always be cached. In that case, there will be an opportunity to avoid the table cache look-up while Get() and NewIterator(). We define options.max_open_files = -1 to be the mode that table readers for live files will always be kept. In that mode, table readers are cached in FileMetaData (with a reference count hold in table cache). So that when executing table_cache.Get() and table_cache.newInterator(), LRU cache checking can be by-passed, to reduce latency. Test Plan: add a test case in db_test Reviewers: haobo, kailiu Reviewed By: haobo CC: dhruba, igor, leveldb Differential Revision: https://reviews.facebook.net/D15039
85 lines
3.1 KiB
C++
85 lines
3.1 KiB
C++
// Copyright (c) 2013, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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//
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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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//
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// Thread-safe (provides internal synchronization)
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#pragma once
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#include <string>
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#include <stdint.h>
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#include "db/dbformat.h"
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#include "rocksdb/env.h"
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#include "rocksdb/cache.h"
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#include "port/port.h"
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#include "rocksdb/table.h"
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namespace rocksdb {
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class Env;
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struct FileMetaData;
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class TableCache {
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public:
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TableCache(const std::string& dbname, const Options* options,
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const EnvOptions& storage_options, int entries);
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~TableCache();
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// Return an iterator for the specified file number (the corresponding
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// file length must be exactly "file_size" bytes). If "tableptr" is
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// non-nullptr, also sets "*tableptr" to point to the Table object
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// underlying the returned iterator, or nullptr if no Table object underlies
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// the returned iterator. The returned "*tableptr" object is owned by
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// the cache and should not be deleted, and is valid for as long as the
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// returned iterator is live.
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Iterator* NewIterator(const ReadOptions& options,
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const EnvOptions& toptions,
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const FileMetaData& file_meta,
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TableReader** table_reader_ptr = nullptr,
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bool for_compaction = false);
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// If a seek to internal key "k" in specified file finds an entry,
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// call (*handle_result)(arg, found_key, found_value) repeatedly until
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// it returns false.
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Status Get(const ReadOptions& options,
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const FileMetaData& file_meta,
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const Slice& k,
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void* arg,
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bool (*handle_result)(void*, const Slice&, const Slice&, bool),
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bool* table_io,
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void (*mark_key_may_exist)(void*) = nullptr);
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// Determine whether the table may contain the specified prefix. If
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// the table index or blooms are not in memory, this may cause an I/O
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bool PrefixMayMatch(const ReadOptions& options, uint64_t file_number,
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uint64_t file_size, const Slice& internal_prefix,
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bool* table_io);
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// Evict any entry for the specified file number
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void Evict(uint64_t file_number);
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// Find table reader
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Status FindTable(const EnvOptions& toptions, uint64_t file_number,
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uint64_t file_size, Cache::Handle**, bool* table_io=nullptr,
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const bool no_io = false);
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// Get TableReader from a cache handle.
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TableReader* GetTableReaderFromHandle(Cache::Handle* handle);
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// Release the handle from a cache
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void ReleaseHandle(Cache::Handle* handle);
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private:
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Env* const env_;
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const std::string dbname_;
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const Options* options_;
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const EnvOptions& storage_options_;
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std::shared_ptr<Cache> cache_;
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};
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} // namespace rocksdb
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